In general, automatic developing machines or processors are often utilized for the development of silver halide photosensitive material from the standpoints of quickness and ease of operation and handling. The processors involve a series of steps of development, fixation, washing and drying. There is an increasing demand for more rapid development. One typical means for accelerating development is to increase the activity of developer. For the rapid development of black-and-white photosensitive material, the activity of developer may be increased by increasing the concentration of a developing agent or increasing the pH of the developer. It is, however, difficult to maintain the developer active because the developer undergoes substantial degradation by air oxidation. Another approach for rapid processing is made from the aspect of photosensitive material. Reducing the thickness of photosensitive material (e.g., protective layer) is effective for rapid processing.
It is well known from early days to use sulfites in order to prevent degradation of developer. When the sulfites which are capable of dissolving silver halides are added to developer, silver can be dissolved from the photosensitive material into the developer as a silver sulfite complex. As the silver complex is reduced in the developer, silver gradually deposits and accumulates on the developing tank and rollers. This is known as silver sludge or stain. Since silver sludge can deposit on photosensitive material being processed thus staining images, the processor should be washed at intervals, that is, periodic maintenance is necessary. If the amount of sulfite added is increased, the amount of dissolving out silver sulfite complex is also increased and the degree of silver sludging is accordingly increased, offsetting the benefits of rapid processing.
One known method for reducing silver sludging is by adding a compound capable of diminishing silver ions dissolving into the developer and/or controlling reduction of silver ions into silver as disclosed in Japanese Patent Application Unexamined Publication (JP-A) No. 24347/1981. This method, however, inevitably retards development itself and lowers sensitivity. Such a sensitivity lowering is a serious drawback for a photosensitive material/development system which is desired to have as high sensitivity as possible. Although it is quite effective for rapid processing to reduce the thickness of photosensitive material (e.g., protective layer), processing of such relatively thin photosensitive material through the processor on the running mode suffers from the problem that more silver ions are dissolved into the developer, aggravating silver sludging. The method of JP-A 24347/1981 is insufficient in preventing silver sludging. There is a desire for a further improvement.
Japanese Patent Publication (JP-B) Nos. 46585/1981 and 28495/1987 disclose another method for reducing silver sludging by adding select compounds. The compounds described therein have an improved anti-sludging function, but they are not necessarily stable and would immediately lose their activity in the system where the developer is subject to air oxidation. There is a need for a further improvement.
Mercaptopyrimidine compounds are known from early days and some have been utilized in the photographic art. U.S. Pat. No. 3,240,603 and UK Patent No. 957,807 utilize mercaptopyrimidine compounds as fixing agents for silver halides. High pH solutions of mercaptopyrimidine compounds in high concentrations are effective fixers. In fact, at least 8 grams of mercaptopyrimidine compound is used in U.S. Pat. No. 3,240,603.
JP-B 24464/1985 utilizes mercaptopyrimidine compounds in bleach-fixing solution for promoting bleaching action.
German Pat. No. 21 26 297 utilizes mercaptopyrimidine compounds in the second developer of a color reversal system for the purpose of increasing the sensitivity thereof. Exemplary is 2-mercapto-4-hydroxy-6-methylpyrimidine. Evaluating this compound, the inventors found that it is effective for preventing silver sludge from depositing, but to a less extent. There is a need for a further improvement.
U.S. Pat. No. 3,597,199 utilizes mercaptopyrimidine derivatives in the second developer of a color reversal system for the purpose of improving photographic properties. Exemplary is 2-mercapto-4-hydroxy-6-aminopyrimidine. Evaluating this compound, the inventors found that it does not have a satisfactory function of preventing silver sludge.
JP-A 204037/1984 utilizes heterocyclic mercapto compounds in black-and-white developer at pH 11.5 or higher for the purpose of preventing silver sludging. One exemplified compound is 2-mercapto-4-hydroxypyrimidine. Testing this compound, we found that it is not necessarily effective for preventing silver sludging.
JP-B 35493/1973 utilizes heterocyclic mercapto compounds in developers for preventing silver sludging. Exemplary is 2-mercapto-4-hydroxy-6-methylpyrimidine. It is effective for preventing silver sludge from depositing to a less extent as mentioned above.
UK Pat. No. 1,296,161 uses mercaptopyrimidine derivatives in developers of the silver salt diffusion transfer type for the purpose of preventing silver sludging. Exemplary is 2-mercapto-4-hydroxy-6-carboxyquinazoline. Evaluating this compound, the inventors found that it does not have a satisfactory function of preventing silver sludge.
As mentioned above, there are known a number of examples utilizing mercaptopyrimidine compounds in processing solution. Several mercaptopyrimidine compounds are used as fixers in concentrated high pH solution form while some are known as agents for preventing silver sludge. Since heretofore known mercaptopyrimidine compounds are not fully effective for preventing silver sludge, there is a need for a substantial improvement.
JP-B 121854/1989 discloses a black-and-white developer which contains an amino or heterocyclic compound having a group capable of adsorbing silver halide for achieving improved photographic quality and preventing black pepper. Exemplary are 1-morpholinopropyl-5-mercaptotetrazole and 1-morpholinoethyl-2-mercaptoimidazole. These compounds were not found to be fully effective for preventing silver sludge.
Several mercaptotriazine compounds have been used in the photographic art. JP-B 24464/1985 uses a mercaptotriazine in a bleach-fixer for promoting bleaching. JP-A 5334/1974 adds a heterocyclic mercapto compound to a lith developer to thereby remove trailing of photographic high contrast photosensitive material. Exemplary is 2,4,6-trimercapto-1,3,6-triazine. JP-A 204037/1984 discloses a black-and-white developer at pH 11.5 or higher which contains a heterocyclic mercapto compound, for example, 2,4-dimercapto-6-hydroxy-l,3,5-triazine for preventing silver sludge. JP-A 53244/1991 uses mercapto-1,3,5-triazine in a dveloper for preventing silver sludge. An example is 2,4-dimercapto-6-hydroxy-1,3,5-triazine again. Evaluating these compounds, we found that they do not have a satisfactory function of preventing silver sludge.
One prior art well-known image toner is 1-phenyl-5-mercaptotetrazole (see T. H. James, The Theory of the Photographic Process, Ch. 16, page 476) which greatly affects photographic properties such as fog, sensitivity and gradation. There is a desire for a method capable of approximating yellow brown color tone to completely neutral with minimal influence on photographic properties.